[Boatanchors] Diode in Filament supply line

[WDAnderson at aol.com]

Good Evening
 
I obtained a TR3 that was DOA. One of the things that I found was that it  
had 6JB6's in the final instead of 12JB6's and a big diode was wired in series  
to the 12vac filament line to those tubes. Anyone ever see this method of 
making  a 6v filament work in a 12v application?
 
73,
 
Wayne
 
VE3XAZ/WA7LZC